The invention generally relates to ropes, wires (cables), wire ropes and assemblies thereof (also referred to as a cable or cable assembly). Additionally, the invention more specifically relates to a wire, wire rope, cable or cable assemblies useable with safety restraint products including seat belt buckle assemblies and pretensioners (which are also referred to in the art as belt tighteners).
Reference is made to FIGS. 1 and 2, which illustrate the construction of a typical wire rope (cable) 20. The wire rope 20 typically includes a core 22, which can be a solid wire or of a multi-strand construction of small diameter wires. The core 22 can be metal, a resin-based material or a naturally occurring material such as wood, cotton, etc. The wire rope or cable 20 additionally includes a plurality of exterior strands 24 wound about the core 22. In many applications, each exterior strand 24 can be formed of a plurality of thin wires 26 or by a single wire. For the purpose of illustration, the wire rope 20 shown in FIGS. 1 and 2 is of conventional construction and comprises a multi-wire stranded core 22 and five external multi-wire strands 24 twisted about the core 22. The lay of the wires relative to each strand as well as the lay of each strand 24 relative to the core 22 will vary with application. The number of wires in a given strand, as is known in the art, will vary from about 3-19.
Additionally, each strand 24 and each wire 26 (of a strand) has a general circular cross-section (see in FIG. 2), however other individual wire (and strand) cross-sectional shapes are acceptable for the present invention.
As can be seen from FIG. 2, there will, in general, exist small spaces 27 between adjacent strands as well as smaller spaces 27a between each adjacent individual wire 26. This spacing typically arises because of the arcuate (circular) cross-sectional shape of the individual wires 26 in each strand 24 as well as the composite shape of each strand 24. As can be appreciated, as the diameter of each of the individual wires 26 is reduced the overall shape of the strands 24 becomes more circular. For the purpose of illustration, each of the multi-wire strands 24 in FIG. 2 is surrounded by a line 32. In one context, the line 32 is an approximation of the general outer circular shape of each strand 24 formed using multiple wires 26. If however, the wire rope cable 20 is made up of a solid core surrounded by solid exterior strand wires (in place of the multi-wire strands), then the line 32 would, of course, show the actual profile of each wire/strand. However, even with the use of solid strands (each with an arcuate cross-sectional shape) the intra-strand spacing 27 will continue to exist.
Returning to FIG. 1, any segment (regardless of length) of wire rope/cable 20 will generally include a first end 34 and an opposite or second end 36, which can be connected to a variety of cooperating mechanisms or couplings in a variety of ways. The length of any segment of wire rope will vary with application.
Reference is briefly made to FIG. 3, which illustrates one known type of application for a wire rope or cable 20 as part of a seat belt system and more particularly as part of an anchor mechanism or seat belt buckle presenting mechanism (for a seat belt buckle 42). In this application, end 36 is connected to a buckle anchor via a ferrule (or some other connection or termination mechanism) 40, which in turn is connected to or is part of a seat belt buckle 42. Opposite end 34 of the segment of wire rope 20 is connected to a floor anchor mechanism 46, which may include another ferrule 44. This arrangement permits the wire rope 20 to be anchored to a structural component of the vehicle, such as the vehicle floor 48 or seat 50). As is known in the art the buckle 42 is mounted adjacent a vehicle seat 50 and positioned at or held at a preferred orientation. One of the benefits of using a wire rope, even a thin rope, is that it is lightweight and extremely strong when subjected to tension forces. However, in seat belt applications if the overall gauge of the wire rope 20 is relatively thin the wire rope will obviously be flexible and will bend even when loaded by a typical seat belt buckle. For example, a seat belt buckle is often anchored by wire ropes having diameters in the range of 2.0-4.0-6.0 mm, which show a propensity to easily bend.
In the configuration of FIG. 3, the seat belt buckle 42 will fall (as an unsupported thin wire rope 20 will bend under the weight of the buckle) to a position illustrated by phantom line 51. To maintain the seat belt buckle in its in desired orientation relative to the seat 50 and to prevent the wire rope 20 from bending, it is common practice to surround the cable with a semi-rigid plastic sleeve or jacket shown by phantom line 52. In essence, the plastic sleeve 52 presents the seat belt buckle 42 in a desired orientation. As will be seen below, one of the advantages of the present invention is the elimination of the need for a sleeve 52 while retaining the ability to present the buckle at known orientations. One of the further disadvantages of wire rope of the type illustrated in FIGS. 1 and 2 is that it has a “memory”, that is, it will not easily take a permanent curvature and therefore easily returns to its original shape after it is bent.
Reference is made to FIG. 4, which shows another use for a wire rope or cable assembly such as 60, which has been incorporated into a known type of seat belt tightener 70 (also referred to in the art as a pretensioner). In a broad sense a pretensioning mechanism also anchors the seat belt buckle. This cable assembly 60 comprises the wire, wire rope or cable 20 terminated at one end 36 at the buckle anchor 40, which is connected to or is formed as part of a frame of a seat belt buckle 42. The other end 34 of the cable 20 is terminated at a piston 68. The pretensioner 70, which is of known design, additionally comprises a tubular housing 72 (which supports the piston) extending from a propellant or generant housing 74 and a bracket section 75. Mounting bracket section 75 is connected to the generant housing 74. A quantity of propellant 76 is located within the generant housing 74 such that when the propellant burns the gases produced propel the piston 68 rapidly down the tube 72, forcibly pulling the cable 20 into the pretensioner 70, which pulls the buckle 42 toward the pretensioner. The downward movement of the buckle reduces slack in the seat belt (not shown) about the occupant. The operation of pretensioners is well known.
Characteristically many buckle belt tighteners such as 70 include a direction changing mechanism 80 such as a pulley, pulley wheel or pulley segment, all of which are denoted by numeral 82. The pulley 82 is secured to or is part of the bracket section 75. As can be seen, the medial section 84 of the cable 20 is looped about (in contact with, threaded through) the pulley 82. The pretensioner 70 includes a guard(s) 86 that functions to prevent the cable from moving off from the pulley 82. In some pretensioners the guard 86 is realized by stand-offs or stops, which are formed (often as bent tabs) as part of the bracket 75 or as part of the pulley 82. These stand-offs or guards 86 define, in cooperation with the pulley 82, a channel in which the cable 20 resides and, as mentioned, the stand-offs or guards maintain the flexible cable in proximity to the surface of the pulley. U.S. Pat. No. 5,911,440 shows one prior buckle pretensioner. Additionally, as can be appreciated, the placement of the guards 86 about the pulley defines the departure angles the cable 20 makes with the pulley. In use within a pulley, the initially straight though flexible cable is easily bent by hand and positioned about the pulley. The channel for the cable can also be machined into mating pretensioner parts as shown in Canadian patent 2158901.
The typical belt tightener (pretensioner) such as 70 will move the buckle a distance to 100 mm within a few milliseconds. As can be appreciated the seat belt buckle experiences extremely high levels of acceleration as the buckle begins to move and subsequent high levels of deceleration as it is brought to a rapid stop (when the piston stops moving or as the buckle engages the bracket 75). To lessen the magnitude of the deceleration to which the buckle is subjected at the end of the pretensioner stroke, the prior art has proposed the use of energy absorption (also called energy dissipation) mechanisms. These mechanisms operate to reduce the velocity (and hence the terminal level of deceleration) the buckle experiences.
The pretensioner 70 of FIG. 4 includes one such energy absorbing mechanism in the form of a thin-walled tube 90, which is made as an integral part of ferrule 40. This tube can also be a separate part positioned loosely about the cable and might be located remote from the ferrule 40. As the ferrule 40 is pulled into contact with the pulley 82 and pulley housing/bracket 75, the tube 90 deforms.
The prior art shows the thin-walled tubing 90 bending along predefined regions as though it were a bellows but not entering the spacing or channel 87 between the guards, tabs or stands-offs 86 and the pulley 82 (or the pulley housing 80). Other proposals permit the thin-walled tubing such as 90 to be pulled into the curved channel 87 in the bracket 75 and dissipate energy as the tube is pinched or diametrically bends as it enters the channel narrower between the bracket 75 and the pulley 82.
It is an object of the present invention to provide an improved rope, wire rope or cable assembly. A further object of the present invention is to provide a method of increasing the stiffness of all or a portion of the wire rope or a segment thereof. A further object of the present invention is to incorporate a wire rope of predetermined stiffness that dissipates energy as the increased stiffness portion of the wire rope is pulled around a pulley. It is a further object of the invention to provide an improved pretensioner or improved anchor assembly.
Accordingly the invention comprises: an improved wire rope or cable or an assembly including such a rope or cable. Additionally, the invention includes various devices which use such a cable or cable assembly including a vehicle occupant restraint system having a seat belt pretensioner comprising a curved cable guide and a flexible wire rope or cable, the rope or cable having a determinable stiffness to bending, positioned about and movable relative to the cable guide, one end of the cable (or wire rope) adapted to be connected to a first means for moving the cable and an opposite end of the cable adapted to be operably connected to a seat belt buckle, a portion of the cable configured to be drawn into the cable guide, such portion being impregnated with a first material to increase the stiffness of the cable.
Many other objects and purposes of the invention will be clear from the following detailed description of the drawings.